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Methods and Treatments to Prevent Cavitation in High Pressure Pumps

IP.com Disclosure Number: IPCOM000239291D
Publication Date: 2014-Oct-27
Document File: 7 page(s) / 431K

Publishing Venue

The IP.com Prior Art Database

Abstract

Cavitation is defined as the process of formation and disappearance of the vapor phase of a liquid when it is subjected to reduced and subsequently increased pressures. Cavitation will occur when the net pressure in the fluid is less than the vapor pressure of the fluid. Typically for hydraulic reciprocating pumps used in the fracturing operation, cavitation causes or may cause performance loss (head drop), material damage (cavitation erosion), vibrations, noise and vapor lock (if suction pressure drops below break-off value). This phenomenon can be extremely destructive to pump life. Cavitation can cause pitting of the connecting rod, valve seat and inserts, and pump casing. In some instances, cavitation has been severe enough to wear holes in the casing and damage the valve seat and inserts to such a degree they becomes totally ineffective. More importantly, the pump efficiency will decrease significantly during cavitation as damage to the valves increases. Methods and treatment to minimize and help prevent cavitation damage by employing new state-of-the-art materials and methods are provided. The materials solution is particularly attractive because it does not involve detailed engineering studies, new pattern equipment, or long lead times. The properties and engineering characteristic of these alloys and materials are described regarding its applicability.

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Methods and Treatments to Prevent Cavitation in High Pressure Pumps

Abstract

Cavitation is defined as the process of formation and disappearance of the vapor phase of a liquid when it is subjected to reduced and subsequently increased pressures. Cavitation will occur when the net pressure in the fluid is less than the vapor pressure of the fluid.

Typically for hydraulic reciprocating pumps used in the fracturing operation, cavitation causes or may cause performance loss (head drop), material damage (cavitation erosion), vibrations, noise and vapor lock (if suction pressure drops below break-off value).

This phenomenon can be extremely destructive to pump life. Cavitation can cause pitting of the connecting rod, valve seat and inserts, and pump casing. In some instances, cavitation has been severe enough to wear holes in the casing and damage the valve seat and inserts to such a degree they becomes totally ineffective. More importantly, the pump efficiency will decrease significantly during cavitation as damage to the valves increases.

Methods and treatment to minimize and help prevent cavitation damage by employing new state- of-the-art materials and methods are provided. The materials solution is particularly attractive because it does not involve detailed engineering studies, new pattern equipment, or long lead times. The properties and engineering characteristic of these alloys and materials are described regarding its applicability.

Introduction

Cavitation damage is a chronic problem leading to impaired pump performance and eventual failure in a wide range of industrial applications. Although primarily mechanical in nature, cavitation damage is more severe in environments where this mechanism acts synergistically with corrosion. The cavitation process damages protective oxide films, exposing unprotected new surface to corrosion. Cavitation occurs when the local pressure of the fluid is reduced to the vapor pressure. Bubbles form in low pressure areas and are swept into regions of higher pressure where they collapse at the metal surface. This collapse is accompanied by release of very high kinetic energy and impact loading on the surface. The impact loading, which is a series of discrete events occurring in a time frame of microseconds, produces relatively high stresses and strains on the metal surface. The cumulative effect leads to the initiation of fatigue cracks. These cracks intersect, causing small fragments of the metal surface to be dislodged leaving the surface in a spongy, porous condition.

Cavitation is a phenomenon which can seriously impact performance and operation of pumps. Predicting new material treatment to control cavitation is an important topic, not only for pumps, but for fluid machinery in general.

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Description

High pressure well service pumps are categorized as reciprocating, positive displacement, single acting plunger pumps. High pressure pumps are used to supply proppant/slurry for...